let K' = a stationary rigid rod. let its length be L (the length between the two ends A and B of K' using a measuring-rod). the axis of K' is lying along the x-axis of a stationary system of coordinates K. let K be provided with clocks which synchronize. let a constant speed v in the direction of increasing x be imparted to K'. let rAB = the distance (as measured by the measuring-rod already employed to measure L) between two points on the x-axis of K where the two ends A and B of K’ are located at a definite time. let clocks be placed at the two ends A and B of K’, and let these clocks synchronize with the clocks of K let a ray of light depart from A at tA in the direction of B, and let the ray of light be reflected at B at tB and reach A again at t’A. time here denotes time of K and also position of hands of the moving clock at the place under discussion. observers moving with K' would declare that (tB - tA) = rAB/(c - v) is not equal to (t’A - tB) = rAB/(c + v). while observers in K would declare that (tB - tA) = rAB/(c - v) = (t’A - tB) = rAB/(c + v). if L = 299,792,458 meters, and v = 0.5*c, what is the value of (tB - tA) and (t’A - tB) using the lorentz transformations if the observers are moving with K'? and if L = 299,792,458 meters, and v = 0.5*c, what is the value of (tB - tA) and (t’A - tB) using the lorentz transformations if the observers are in K? thanks. i think the answer is going to help me understand the lorentz transformations and how to apply them in order to understand relativity of lengths and times. thanks again.